This disclosure relates to a memory system, and more particularly, to a memory system comprising memories with different capacities and storing and reading method thereof.
A memory is an essential component of many kinds of electronic devices. In the early days, memories were independently soldered onto an electronic device's main board, or independently plugged into sockets that were soldered onto the main board. This scheme worked fine since electronic devices in the early days did not require much memory space. However, as the requirements of memory space and memory bandwidth increased, the number of memories demanding space on a main board of an electronic device was also increased. To deal with this problem, an idea of integrating a plurality of memories and supporting components into a single apparatus, which is referred to as a memory system, had been proposed.
In a memory system of the related art, memories with equal capacity must be used. FIG. 1 shows a block diagram of a conventional memory system 100. The memory system 100 includes a memory controller 110, a first memory 120, and a second memory 130. The capacity of the first memory 120 is equal to the capacity of the second memory 130. Both the first memory 120 and the second memory 130 have a data bus width of N and a control and address bus width of M. As for the memory controller 110, since the data buses of the two memories are shunted and the control and address buses of the two memories are shared, the memory controller 110 has a data bus width of 2N and a control and address bus width of M.
Since memories with equal capacity must be used in a memory system, the total capacity of a memory system of the related art does not have flexibility. For example, if a 48 megabytes (MB) capacity is required, it is not allowed to assemble a first memory of 16 MB capacity with a second memory of 32 MB capacity to build a memory system. Instead, two memories each of 32 MB capacity must be used to build the memory system, even though the excess 16 MB of memory space is not required. The cost of the whole memory system is therefore increased.